1. Field of the Invention
The present invention relates to a power converter. More specifically, the invention relates to an inverter or DC-AC converter which converts DC drive power to AC power to drive a motor connected to the wheels of an electric car.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. Hei. 5-219607 discloses a power converter mounted around the motor drive shaft of a motor in an electric car. More specifically, this system includes a motor in a substantially cylindrical shape and a drive shaft protruding from one end of the motor which transmits the motor torque to the wheels of the electric car. In that system, the inverter is mounted on the end of the motor opposite the shaft.
In systems using a single shaft motor as described above, the processes of removing and installing the inverter are relatively trouble-free since the side of the motor opposite the shaft is flat and there are no members which might restrict the seating of the inverter. However, when using a dual shaft motor on which the motor shaft extends from both ends to drive respective vehicle wheels, the shaft obstructs the mounting of the inverter so that it is impossible to mount it on an end of the motor like a conventional single shaft motor. In most cases, since the motor shaft generally protrudes from the center on the side end face of the motor, a doughnut-shaped inverter may be provided to avoid interference with the centrally located shaft. However, if this structure is used in an electric car, it is impossible to remove or install the inverter while the shaft is connected to a load such as the vehicle's wheels; thus, that the inverter cannot be maintained, inspected or replaced while it is mounted on the vehicle.